Re: simpler query significantly slower

twanger@smartvia.de writes:
>     select
>         distinct
>         gruppen_produkte.produktgruppen_id
>     from
>         r_gruppen_produkte
>     where
>         r_gruppen_produkte.gruppen_id = gruppen.gruppen_id             // this and the next cond are removed in 2nd
query
>     and
>         gruppen.parent_id=1
>     and
>         r_gruppen_produkte.gruppen_id = r_personen_bereiche.g_id
>     and
>         r_personen_bereiche.p_id = 1234

This SQL seems rather seriously confused.  It looks to me like you will
get back one copy of each distinct produktgruppen_id value appearing in
gruppen_produkte.  Since no gruppen_produkte field is constrained by
WHERE, none will be eliminated.  All that the rest of the query does is
cause a completely useless Cartesian-product join against some subset
of r_gruppen_produkte * gruppen * r_personen_bereiche.

Possibly you meant to select from r_gruppen_produkte.

BTW, PG 7.1 would have complained about the lack of FROM entries for
gruppen_produkte, gruppen, and r_personen_bereiche, which might have
clued you to your error ...

            regards, tom lane